Human visual performance depends on parallel functional channels established in the early stages of visual processing. Each psychophysically defined channel may depend on contributions from several types of ganglion cell. In turn, the contribution from each type of ganglion cell depends on the structure of its array and its wiring to specific types of photoreceptor. Our broad goal is to determine the retinal microanatomy that underlies these psychophysical and physiological aims are: 1) Identify in the foveal region of the primate (macaque) retina, which closely resembles the human, all the types of on ganglion cell that are present. 2) Determine the array structure of each type. 3) Determine the detailed connections of each type with rods and chromatically identified cones. 4) Incorporate this information into computational models that simulate ganglion cell performance under different conditions of luminance and spectral composition. These findings will provide a basis for linking the anatomical circuitry to the physiology and psychophysics. Our strategy is to study intensively a small patch of retina just off the foveal center, where spatial acuity is high, yet rods are also present, and where ganglion cells are stacked in multiple ranks. We will prepare the tissue in two series of ultrathin sections, one radial and the other tangential, photograph them in the electron microscope, and create complete photographic montages of each. We shall use the radial series to identify types and their circuitry and the tangential series to study the structure of the various arrays.